Often, it is useful to measure the angular displacement and/or torque between two members, such as two rotating shafts. One shaft rotates relative to the other shaft and a sensor, such as a torque sensor, detects the angular displacement and/or torque between the two shafts. Also, it is often useful to measure the absolute angle of rotation of a rotating shaft, where the shaft rotates and an angle sensor detects the angle of the shaft relative to a stationary point. These measurements are useful in systems, such as power steering systems in trucks and automobiles.
Typically, in power steering systems, a first shaft is connected to a steering wheel and a second shaft is connected to a steering mechanism. The first shaft is connected to the second shaft via a compliant member, such as a torsion bar. The driver turns the steering wheel, which rotates the first shaft a number of degrees with respect to the second shaft. A torque sensor senses the angular displacement of the first shaft relative to the second shaft and provides an output indicating the torque applied to the first shaft, the torsion bar, and the second shaft. The amount of power steering assist is determined as a function of the applied torque. A separate angle sensor senses and outputs the angle of rotation of the first shaft or the second shaft.
These systems can be magnetic based systems, contact based systems that use, for example, resistive tracks and wipers, inductive systems, or optical systems. In some magnetic based systems, the torque sensor and the angle sensor are separate sensors. Where, the torque sensor includes materials, such as multiple magnets, and the angle sensor includes materials, such as one or more magnets. Multiple magnets and separate sensors increase the cost and complexity of the system.
For these and other reasons there is a need for the present invention.